This invention relates to a mechanical prosthesis for replacement of a ligament between two bones in the human body. Within the context of this invention, ligaments are defined as bands of fibrous tissue connecting articulated bones.
The primary function of these ligaments is to provide restraints to the movement of one bone relative to another. During body movement, tensile loads are imposed on the ligaments. The rotation of one bone relative to another that occurs with this articulation also causes bending in the ligaments. The loss of or damage to these ligaments leads to abnormal joint movement and disability.
Current ligament prostheses attempt to mimic the natural ligament through the use of flexible materials. These materials possess different physical properties than the natural ligament. Failure in these prostheses has often been due to inadequate tensile strength or loss of tensile strength with time. Even if the initial strength of the material is adequate, the physical geometry of the prosthesis dictated by attachment to bone and by joint flexion may lead to failure through fatigue, abrasion, and cutting against bone surfaces.
Previous authors have taught the use of prosthetic joints with bearing surfaces to replace a natural joint in the body. Unlike these prior references, the present invention involves the use of mechanical elements, that is, a combination of links and bearings to preserve the joint and restore normal movement.